Roll mills, particularly material bed roll mills, are used particularly advantageously for the comminution of mineral material, for example cement raw materials, cement clinker, ores or the like, that is to say relatively brittle and highly abrasive bulk materials. In order during material bed comminution to be able to maintain a predetermined grinding gap between the two rollers and thus above all to maintain a minimum basic gap, distance pieces are generally provided between the adjacent bearing jewels which rotatably support the rolls. As a function of the grinding process wear occurs on the roll surfaces, so that with a fixed setting of the distance pieces the basic grinding gap between the two rolls would become increasingly larger, which has a negative effect on the grinding process. In order to prevent this, adjustable distance pieces are generally provided between the bearing jewels which are adjacent to one another.
In a quite simple known construction of distance pieces, these can be provided for instance in the form of sets of plates or the like, so that these distance pieces can be infinitely adjusted by the removal of plates.
Furthermore, it is also known in the art to construct distancing arrangements in the form of spindle drive arrangements which each comprise an adjusting spindle and a spindle nut and can be infinitely adjusted by turning the spindle or the nut. In this case in the region between two fixed and floating bearing jewels arranged adjacent to one another the spindles can be rotatably mounted with one end on the inner end face of the fixed bearing jewel and can be provided with a drive chain wheel, whilst the opposite end of the spindle is in screwed engagement with a spindle nut arranged on the inner end face of the floating bearing jewel, aided by a separate protection against torsion.
The disadvantages of these known distance piece constructions may be seen above all in the fact that they are arranged essentially between the fixed and floating bearing jewels which are arranged adjacent to one another and that they usually require a relatively large minimum installation space, as a result of which a maximum possible wear path cannot be optimally utilised when the rolls are moved together in order to maintain the grinding gap. Moreover, it is frequently necessary to interrupt the grinding process when the grinding gap is being newly set, so that undesirable shutdown times must be accepted.
Therefore in such a roll mill it is desirable that the distance pieces of the distancing arrangement should satisfy as many as possible of the following requirements:
in order to be able to utilise fully the maximum possible thickness of the wear layer, the fixed and floating bearing jewels which are arranged adjacent to one another should be able to be moved together until they touch; PA1 with a view to an optimum grinding process the basic setting (basic gap) of the grinding gap is very important, so that the distance pieces should be infinitely adjustable; PA1 in order as far as possible to avoid shutdown times, even in the case of roll mills operated in a continuous process, the distance pieces should be adjustable without difficulties from the exterior or automatically by way of their distancing arrangements; PA1 the distance pieces should not exert any additional tipping moments on the bearing jewels.